1. Field of the Invention
The present invention pertains generally to land vehicles, and more particularly to articulated vehicles that incorporate both a ball coupling and a draft pin coupling in a single unitary hitch.
2. Description of the Related Art
Multi-purpose trailer hitches have been desired for many years, particularly in the agricultural field. This is a direct consequence of the prevalence of multi-purpose vehicles, including for example but not limited to such vehicles as pick-up trucks, tractors and all-terrain vehicles. These machines have gained wide acceptance in the field of agriculture, since a single vehicle may provide both human transport and the movement of one or more very diverse loads. As a more detailed but not limiting example, a person may use a pick-up truck to travel over a roadway to a remote field or the like, whether the roadway is paved or otherwise. The pick-up will be generally preferred for this activity, owing to the comfort of the driver and any passengers, and also owing to the design for relative speed and safety for this type of travel. Once at the remote field location, the person may then discover the need to move a trailer or the like. As an example, feeder trailers are in common use which may have been emptied unexpectedly or which may require movement for other unexpected reasons. Rather than returning to the remote vehicle storage area and returning with a tractor, which is much more specifically designed for the moving of implements and agricultural trailers, the person would much prefer to directly couple the trailer to pick-up truck. Such multi-purpose utility, which is particularly desirable in the field of agriculture but which is required in other industries as well, provides substantial savings of both time and expense. Consequently, there has long been a demand for devices which permit the coupling of various devices to a motorized land vehicle.
Over-the-road trailers, such as but not limited to boat, camper and standard utility trailers., almost universally require a ball for connection to the trailer. In contrast, most agricultural trailers and implements, including but not limited to harrows, planters, spreaders and agricultural wagons, rely upon a pin-type hitch. Consequently, for a towing vehicle to be useful to tow a wide variety of towed vehicles, the towing vehicle must couple through both the ball and pin couplings.
Several patents are exemplary of hitches which provide the broader capability of diverse couplings. Illustrative are U.S. Pat. No. 2,827,307 by Osborn; U.S. Pat. No. 3,801,134 to Dees; U.S. Pat. No. 3,922,006 by Borges; 4,022,490 by Rocksvold; and U.S. Pat. No. 4,729,571 by Tienstra. These patents illustrate various pivotal couplings which, through the pivotal motion, exchange one type of hitch connector for another. Unfortunately, while these pivotal couplings offer extremely flexible coupling through a wide variety of couplers, several limitations have prevented these couplers from becoming the primary hitch of choice. The first limitation is derived directly from the components that permit mechanical motion. For example, in the Osborn patent a set of bolts may be provided which are removed or which may be loosened to permit the necessary pivoting between attachment support and vehicular attachment. This connection suffers very large force concentration during use when the two components are not tightly attached, since the play introduced by the ability to pivot also is associated with physical hammering upon the variation of travel between towing and towed vehicle, such as occurs when a pothole or the like is encountered by either vehicle. This substantial force requires the use of much more expensive components, and may still lead to early fatigue or stress induced cracking. The consequence of early fatigue or failure may be quite serious, and so designs reduce the likelihood of such an event occurring are generally preferred. When the components are instead tightly attached together, the forces are better transmitted without stress and force concentrations, but the desired pivotal motion between components is prevented, and time-consuming and difficult disassembly is required to adapt the hitch from one type of coupler to another. In other words, the very convenience which was intended is lost. Another disadvantage to these types of trailer hitches is the simple economic disadvantage. The construction of these types of hitches requires a number of relatively expensive components, making them economically less desirable.
A more common arrangement of components is illustrated by Edinger in U.S. Pat. No. 3,812,956. In this design, several holes are provided which permit one or more type of coupling to be available. In particular, an implement pin may be used to pass through a hole, or may alternatively placed in a nearby hole for storage. When required, the ball and implement pin may be exchanged, thereby permitting the vehicle operator to exchange one coupling for another. Unfortunately, in this arrangement both the agricultural implement and a ball and socket connections are at a single elevation, which is not the correct elevation for these different types of trailers. Furthermore, the requirement for the removal of the ball from the hole to rearrange once again means the use of substantial tools or the risk of lost or failed coupling, since a ball is normally very tightly bolted in the hole to prevent the motion relative to the hole and associated stress concentrations and fatiguing that were discussed herein above.
Day, in U.S. Pat. No. 3,700,263, illustrates a coupler similar to Edinger, where a first hold may be provided for a ball, and a second hole is provided which may either house a ball or a pin. The first ball connection is elevated sufficiently to just clear the second hole. No attempt is made to provide proper elevation, nor is there nay way to readily store an associated pin while using the ball illustrated therein. What is desired then is a coupler which overcomes the limitations of the prior art by incorporating such desirable features as a low manufactured cost and high field reliability, and which provides optimum coupling for both pin and also ball couplings.